Traditional methods for studying human coronary artery disease have significant limitations. Angiography allows evaluation only of the geometry of the unobstructed part of the lumen; it cannot provide information on the structural of the arterial wall, which is essential to understand the processes leading to plaque rupture. In addition, limitations associated with the projection of three dimensional (3D) structures onto a planar image further hinder this approach. Although histological analysis directly evaluates atherosclerotic plaque composition, it cannot be used to identify plaques "at risk" for rupture because the necessary tissue specimens can only be obtained at autopsy. An emerging technique, intravascular ultrasound (IVUS), can provide the necessary structural information in situ, but only in a two dimensional (2D) format that makes it impossible to study the 3D relationship of arterial wall components. The development and refinement of IVUS have provided a powerful in vivo method to assess plaque morphology. Recent clinical studies have documented the sensitivity of IVUS in detecting atherosclerosis, and it is increasingly employed to assist in selecting an appropriate therapeutic intervention. Perhaps more importantly, the potential of IVUS to quantify the structure and geometry of normal and atherosclerotic coronary arteries will allow one to characterize specific lesions and to distinguish which plaques will or will not lead to coronary plaque rupture. Two primary hypotheses will be tested by this study: (1) IVUS combined with advanced digital image and signal processing provides a sensitive method to determine plaque geometry and composition in the human coronary artery wall; and (2) IVUS can discern specific lesion parameters, providing data that can be used to identify "at-risk" plaques. These hypotheses will be tested by utilizing: (1) IVUS images to characterize the composition and geometry of the coronary artery wall and to correlate the results with a histological "gold-standard"; (2) custom-engineered IVUS analysis software to describe the geometry, composition, and spatial component relationships of the vessel; and (3) determine material behavior of atherosclerotic plaques using finite element based strain field reconstruction technique known as Warping.